Haemolytic Anaemias
Rarely, anaemia is due to problems that cause the red blood cells to break down prematurely. Normally, red cells live in the blood for about 4 months. In haemolytic anaemia, this time is shortened, sometimes to only a few days.

Sickle cell anaemia is an inherited problem that can cause minor difficulties as the "trait" (when you carry one mutated gene from one of your parents) but severe clinical problems as the "disease" (when you carry two mutated genes, one from each of your parents). The red blood cells are misshapen and clog the blood vessels, causing pain and anaemia. Screening is usually done on newborns – particularly those of African descent. Treatment is usually based on the symptoms.

Thalassaemia is an inherited abnormality of haemoglobin production and causes small red blood cells that resemble those seen in iron deficiency. In its most severe form, the red cells have a shortened life span. In milder forms, anaemia is usually mild or absent, and the disease may be detected by finding small blood cells on a routine FBC. This genetic disease is found frequently in people of Mediterranean, African, and Asian heritage. The "minor" form (sometimes called trait, as with sickle cell) occurs when a person inherits half normal genes and half thalassaemia genes. It causes a mild anaemia and no symptoms. The "major" form (due to inheriting all thalassaemia genes) is more severe and may result in growth problems, jaundice (yellowing of the skin and whites of the eyes), and severe anaemia. The haemoglobin electrophoresis shows an increase in haemoglobin A2 and/or haemoglobin F in one form (called beta thalassaemia), but may be relatively normal in the other form.